Hydraulic pump assembly

ABSTRACT

A hydraulic pump assembly having a main pump, a charge pump and an auxiliary pump driven by a single shaft is provided. A pair of hydraulic porting members cooperates to feed and distribute hydraulic fluid between the three pump units, and a single inlet may be used to provide hydraulic fluid to the charge pump and the auxiliary pump.

CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.15/357,817, filed on Nov. 21, 2016, which is a continuation of U.S.patent application Ser. No. 14/792,007, filed on Jul. 6, 2015, now U.S.Pat. No. 9,695,844, which is a continuation of U.S. patent applicationSer. No. 13/480,134, filed on May 24, 2012, now U.S. Pat. No. 9,074,670,which claims the benefit of U.S. Provisional Application No. 61/553,381,filed on Oct. 31, 2011; U.S. Provisional Application No. 61/514,727,filed on Aug. 3, 2011; and U.S. Provisional Application No. 61/490,994,filed on May 27, 2011. The disclosures of all of these priorapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This application relates to pump assemblies generally and, inparticular, to hydraulic pump assemblies intended for use in driving avehicle or utility transport, such as a riding mower, that requiregreater pump capacity for auxiliary functions such as power steering.

SUMMARY OF THE INVENTION

An improved hydraulic pump assembly having a plurality of pumps used fordifferent applications, yet disposed in a compact in-line arrangement,is disclosed herein. A hydraulic pump assembly having an auxiliary pumpin the form of a fixed displacement, axial piston pump suitable for highflow applications is provided. A single shaft drives a main, variablespeed axial piston pump used as a propulsion pump for the vehicle, anassociated gerotor charge pump, and the axial piston auxiliary pump. Apair of port blocks, or end caps, cooperates to feed and distributehydraulic fluid between the three pump units and external hydraulicdevices to provide, for example, a source of propulsive fluid to ahydraulic wheel motor and an auxiliary unit such as a power steeringunit, a debris collection unit, or the like. The present inventionimproves the auxiliary pump capacity over that of more conventionalauxiliary gear pumps.

The disclosed arrangement places all three of these pumps in a compactin-line arrangement that allows all three different pumps to be poweredby a single input shaft. Prior art designs such as commonly owned U.S.Pat. No. 7,257,948 use a pair of propulsion pumps but do not provide fora single propulsion pump in-line with both an auxiliary pump and acharge pump to provide additional charge fluid to the system. A betterunderstanding of the objects, advantages, features, properties andrelationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forthillustrative embodiments that are indicative of the various ways inwhich the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a first representative hydraulic pumpassembly.

FIG. 2 is an exploded, isometric view of the hydraulic pump assembly ofFIG. 1.

FIG. 3 is a top view of the hydraulic pump assembly of FIG. 1.

FIG. 4 is a partial section view of the hydraulic pump assembly of FIG.3 along the line 4-4.

FIG. 5 is a partial section view of the hydraulic pump assembly of FIG.3 along the line 5-5.

FIG. 6 is a side elevation view of the end cap of the main, axial pistonpump of the hydraulic pump assembly of FIG. 1.

FIG. 7 is a section view of the end cap of FIG. 6 along the line 7-7with some elements shown whole for clarity.

FIG. 8 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 1.

FIG. 9 is a section view of the end cap of FIG. 8 along the line 9-9.

FIG. 10 is a top view of a second embodiment of a representativehydraulic pump assembly.

FIG. 11 is a partial section view of the hydraulic pump assembly of FIG.10 along the line 11-11.

FIG. 12 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 10.

FIG. 13 is a section view of the end cap of FIG. 12 along the line13-13.

FIG. 14 is a top view of a third embodiment of a representativehydraulic pump assembly.

FIG. 15 is a partial section view of the hydraulic pump assembly of FIG.14 along the line 15-15.

FIG. 16 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 14.

FIG. 17 is a section view of the end cap of FIG. 16 along the line17-17.

FIG. 18 is a top view of a fourth embodiment of a representativehydraulic pump assembly.

FIG. 19 is a partial section view of the hydraulic pump assembly of FIG.18 along the line 19-19.

FIG. 20 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 18.

FIG. 21 is a section view of the end cap of FIG. 20 along the line21-21.

FIG. 22 is a top view of a fifth embodiment of a representativehydraulic pump assembly.

FIG. 23 is a partial section view of the hydraulic pump assembly of FIG.22 along the line 23-23.

FIG. 24 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 22.

FIG. 25 is a section view of the end cap of FIG. 24 along the line25-25.

FIG. 26 is a top view of the end cap of FIG. 24.

FIG. 27 is a section view of the end cap of FIG. 26 along the line27-27.

FIG. 28 is a top view of a sixth embodiment of a representativehydraulic pump assembly.

FIG. 29 is a partial section view of the hydraulic pump assembly of FIG.28 along the line 29-29.

FIG. 30 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 28.

FIG. 31 is a section view of the end cap of FIG. 30 along the line31-31.

FIG. 32 is a top view of the hydraulic pump assembly of FIG. 28 with theauxiliary pump housing and the auxiliary pump removed.

FIG. 33 is a partial section view of the hydraulic pump assembly of FIG.32 along the line 33-33 with a portion of the main pump housing removed.

FIG. 34 is a top view of a seventh embodiment of a representativehydraulic pump assembly.

FIG. 35 is a partial section view of the hydraulic pump assembly of FIG.34 along the line 35-35.

FIG. 36 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 34.

FIG. 37 is a section view of the end cap of FIG. 36 along the line37-37.

FIG. 38 is a top view of the auxiliary pump end cap of FIG. 36.

FIG. 39 is a section view of the end cap of FIG. 38 along the line39-39.

FIG. 40 is a section view of the end cap of FIG. 38 along the line40-40.

FIG. 41 is a top view of an eighth embodiment of a representativehydraulic pump assembly.

FIG. 42 is a partial section view of the hydraulic pump assembly of FIG.41 along the line 42-42.

FIG. 43 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 41.

FIG. 44 is a section view of the end cap of FIG. 43 along the line44-44.

FIG. 45 is a top view of a ninth embodiment of a representativehydraulic pump assembly.

FIG. 46 is a top view of a tenth embodiment of a representativehydraulic pump assembly.

FIG. 47 is a partial section view of the hydraulic pump assembly of FIG.46 along line 47-47.

FIG. 48 is a side elevation view of the auxiliary pump end cap of thehydraulic pump assembly of FIG. 46.

FIG. 49 is a section view of the end cap of FIG. 48 along line 49-49.

FIG. 50 is a schematic of a vehicle incorporating the tenth embodimentof the hydraulic pump assembly.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the present invention in accordance with itsprinciples. This description is not provided to limit the invention tothe embodiments described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiments describedherein, but also other embodiments that may come to mind in accordancewith these principles. The scope of the present invention is intended tocover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers or serial numbers in cases where such labelingfacilitates a more clear description. For example, the auxiliary pumpend caps in the various embodiments disclosed herein are seriallynumbered as 42, 142, 242, 342, 442, 542, 642, 742, 842 and 942respectively, to ease recognition. Additionally, the drawings set forthherein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. As stated above, the present specification is intended to betaken as a whole and interpreted in accordance with the principles ofthe present invention as taught herein and understood by one of ordinaryskill in the art.

The description that follows illustrates representative hydraulic pumpassemblies in accordance with the principles of the invention. In each,a unique embodiment of an axial piston auxiliary pump is mated to astandardized configuration of a main, axial piston pump and anassociated gerotor charge pump. The design, layout and function of themain, axial piston pump and its end cap porting can be substantiallysimilar to that illustrated in U.S. Pat. No. 6,332,393, the disclosureof which is incorporated herein by reference in its entirety, and assuch, will not be described in detail. Differences in the design, whereimportant to an understanding of the present invention, will beaddressed herein. Other variable speed hydraulic pumps known in the artare contemplated within the scope of the invention.

FIGS. 1-9 detail a representative hydraulic pump assembly 10 having anauxiliary pump 40 assembled to a main pump 20. In general, main pump 20comprises a housing 21 that forms a sump 12 for the main, variable speedpump when sealed by main pump end cap 22. A rotating kit disposed insump 12 comprises a cylinder block 17 having a set of pistons (notshown) that ride on a thrust bearing in a known manner. The displacementof the main pump 20, and the direction of fluid flow into and out ofsystem ports 26 and 27, respectively, is controlled by rotation of atrunnion arm 23 engaged to a swash plate containing the thrust bearing.Pump shaft 30 is axially engaged to the main pump cylinder block 17 andextends from housing 21 at a first end. In a typical application, pumpshaft 30 is driven by a prime mover (not shown), such as an internalcombustion engine or electric motor, by means of a shaft coupled to thefirst end of pump shaft 30 or by means of a pulley and belt arrangement;in either case, the splines 30 c at the first end of pump shaft 30 serveas the means of engagement.

Hydraulic pump assembly 10 further comprises a gerotor charge pump 84engaged to pump shaft 30 and located between main pump end cap 22 andauxiliary pump end cap 42. Charge pump 84 comprises an inner gerotorelement 71 having a spline 71 a engaged to a corresponding spline 30 bon pump shaft 30 to rotate therewith, and an outer gerotor element 70,both disposed on a running surface 73 formed on a face of main pump endcap 22. Running surface 73 is located on the opposite side of main pumpend cap 22 from a running surface (not shown) upon which the main pumpcylinder block is disposed. When the auxiliary pump end cap 42, mainpump end cap 22 and main pump housing 21 are assembled as a unit bymeans of threaded fasteners 29 engaging threaded bores in main pumphousing 21, an o-ring 72 seals the outer and inner gerotor elements, 70and 71 respectively, within a pocket 16 formed in the auxiliary pump endcap 42 and closed off by main pump end cap 22. As described herein, mainpump end cap 22 is sandwiched between main pump housing 21 and auxiliarypump end cap 42. Other means for joining housings and end caps known inthe art, such as bolts and corresponding nuts, are contemplated withinthe scope of the invention. It is also understood that valve plates orthe like may be used between the pumps and the running surfacesdiscussed herein.

The third primary component of hydraulic pump assembly 10 is theauxiliary pump 40 comprising a cylinder block 49 disposed within anauxiliary pump chamber 64 formed by the joining of an auxiliary pumphousing 41 to auxiliary pump end cap 42, accomplished by means ofthreaded fasteners 47. More specifically, cylinder block 49 is rotatablydisposed on an auxiliary pump running surface 52 formed on auxiliarypump end cap 42. Auxiliary pump running surface 52 is located on theopposite side of the auxiliary pump end cap 42 from the side having thegerotor charge pump pocket 16. Auxiliary pump chamber 64 ishydraulically sealed by an o-ring 48 that may have a correspondinglocating feature on one or both of the auxiliary pump housing 41 and theauxiliary pump end cap 42. An axial spline 49 a formed in cylinder block49 engages a corresponding spline 30 a on pump shaft 30 to rotatetherewith. The cylinder block 49 receives a set of pistons 50 that rideon a thrust bearing 51 disposed at a fixed angle within auxiliary pumphousing 41 based on engagement therein with an inclined surface 41 a.The degree of incline corresponds to the amount of displacement producedby this fixed displacement, axial piston auxiliary pump 40. Thedisplacement, depending on the application, can be set by the degree ofincline formed within the auxiliary pump housing 41. The direction ofhydraulic fluid flow, into auxiliary pump inlet port 46 and out ofauxiliary pump outlet port 43, is unidirectional, being fixed by theorientation of the inclined surface 41 a relative to the rotationaldirection of pump shaft 30. Pistons 50 remain engaged to thrust bearing51 throughout their displacement cycle under the bias of piston springs59.

Pump shaft 30 is rotatably supported within main pump housing 21 by aball bearing (not shown), a first journal bearing 81 within the mainpump end cap 22, and a second journal bearing 31 within the auxiliarypump end cap 42. It should be understood that the type of bearingutilized can be changed depending on the application or the duty cycledesired, replacing a journal bearing, for example, with a needlebearing.

The hydraulic porting formed within auxiliary pump end cap 42 and mainpump end cap 22 cooperates to feed and distribute hydraulic fluidbetween the three pump units and any external hydraulic devices linkedto the hydraulic pump assembly 10 in a hydraulic circuit (not shown). Asshown in FIGS. 2 and 4-7, main pump end cap 22 provides the necessaryporting for the main pump 20 and a portion of the necessary porting forthe charge pump 84. Main pump arcuate ports 18 a and 18 b, respectively,on the main pump running surface (not shown) provide fluid communicationbetween the main pump cylinder block and system ports 26 and 27,respectively, via system passages 35 and 36, respectively. System ports26 and 27, representing the high and low pressure sides of main pump 20,are typically placed in fluid communication with an external hydraulicdevice, such as a wheel motor, via hydraulic lines (not shown). A bypasspassage 37 links system passages 35 and 36 to permit, for example,movement of a temporarily disabled vehicle. Bypass passage 37 isnormally closed to fluid communication between system passages 35 and 36by a bypass valve 24 located in bypass port 90, permitting normaloperation of the main pump 20. Main pump end cap 22 varies from thatillustrated in U.S. Pat. No. 6,332,393 in two regards not affecting thefunction described therein. First, the bypass port 90 is orientedperpendicular to system passages 35 and 36, as opposed to paralleltherewith. Secondly, main pump end cap 22 only provides a single drainport 38, as opposed to a pair of drain ports on opposing sides of theend cap. Here, drain port 38 connects to drain passage 39, providing apathway from the sump 12 for main pump 20 to an external location, suchas a reservoir used for cooling.

Main pump end cap 22 further contains a pair of combination check/reliefvalves 25 that function to route make-up fluid, as necessary, from acharge gallery 76 to either of the system passages 35 and 36 thenserving as the low pressure side of main pump 20; and also to providepressure relief from the high pressure side of main pump 20 at apredetermined set point. The structure and function of valves 25 may bein accordance with the teachings of commonly owned U.S. Pat. No.6,719,005, the disclosure of which is incorporated by reference herein,and shall not be further described.

Main pump end cap 22 further comprises a pair of charge pump arcuateports, 74 a and 74 b, on charge pump running surface 73. Charge pumparcuate port 74 a, an inlet port, is connected via inlet passage 32 tomain pump inlet port 83 on the exterior of main pump end cap 22.Typically, main pump inlet port 83 would be placed in fluidcommunication with a return line from an external reservoir or oilcooler. With respect to hydraulic pump assembly 10, however, a threadedinlet port plug 33 closes off main pump inlet port 83. As will bedescribed in greater detail below, charge pump 84 is fed from the inletport 46 of auxiliary pump end cap 42. Charge pump arcuate port 74 b, anoutlet port, provides pressurized hydraulic fluid to charge gallery 76via a pair of connecting charge passages 86. The charge gallery 76 issealed by diagnostic port plug 34 in diagnostic port 28. Charge gallery76 also possesses a bleed passage 80 leading to the sump (not shown) ofmain pump 20 to aid cooling of the hydraulic fluid. A charge pump reliefvalve 75, located in charge relief passage 77, comprises a simple ball75 a and spring 75 b construction retained between the valve seat 77 ain charge relief passage 77 and auxiliary pump end cap 42. Charge pumprelief valve 75 relieves hydraulic fluid to an annular passage 78 formedin auxiliary pump end cap 42 about charge pump 84, the annular passage78 lying adjacent charge pump o-ring 72. From there, the hydraulic fluidis recycled through charge relief inlet passage 79 and main pump inletpassage 32 to charge pump arcuate port 74 a.

As best shown in FIG. 4, auxiliary pump inlet port 46 leads to auxiliarypump inlet passage 55 which intersects both the auxiliary pump arcuateport 53 a and a second, charge pump arcuate port 56 formed in the pocket16 containing charge pump 84. Thus, the auxiliary pump inlet passage 55feeds both the auxiliary pump 40 and the charge pump 84. Additionally,charge pump 84 can be fed from both the main pump end cap 22 and theauxiliary pump end cap 42. Auxiliary pump 40 discharges fluid toexternal hydraulic devices through auxiliary pump outlet port 43 viaauxiliary pump arcuate port 53 b and auxiliary pump outlet passage 58.To balance the flow of hydraulic fluid in the auxiliary pump hydrauliccircuit, the inside diameters of auxiliary pump inlet passage 55 andcorresponding inlet port 46 are larger relative to those of theauxiliary pump outlet passage 58 and its corresponding outlet port 43.As depicted with main pump inlet port 83 plugged, hydraulic pumpassembly 10 is configured to return hydraulic fluid from a reservoir oroil cooler via auxiliary pump inlet port 46, creating an open systemconfiguration for the auxiliary pump hydraulic circuit (not shown). Werethe main pump inlet port 83 to be opened and utilized to returnhydraulic fluid from a reservoir or oil cooler, the auxiliary pumphydraulic circuit could be configured as a closed system.

As shown in FIGS. 8 and 9, the auxiliary pump end cap 42 also possessesan auxiliary pump relief mechanism. An auxiliary pump relief valve 45resides in auxiliary relief valve port 60, preventing unregulated fluidcommunication between auxiliary pump outlet bore 65, which sees thefluid pressure resident in auxiliary pump outlet passage 58, andauxiliary pump relief passage 61, which communicates externally viaauxiliary pump relief port 44. Auxiliary pump relief valve 45 comprisesa threaded plug 45 a that receives a relief spring 45 b, and a ball 45c. When the fluid pressure in auxiliary pump outlet bore 65 exceeds thecracking pressure of relief spring 45 b, auxiliary pump relief valve 45opens and places auxiliary pump outlet passage 58 in fluid communicationwith auxiliary pump relief port 44. Thus, the auxiliary pump reliefsystem of hydraulic pump assembly 10 is designed to relieve hydraulicfluid to an external reservoir or oil cooler.

Normal hydraulic fluid losses by the auxiliary pump 40 that build up inauxiliary pump chamber 64 are removed through an auxiliary pump casedrain 54 best illustrated in FIG. 5. The auxiliary pump case drain 54communicates with annular passage 78, ultimately routing excess fluid tocharge pump arcuate port 74 a.

A second representative hydraulic pump assembly 110 having auxiliarypump 140 assembled to main pump 20 is depicted in FIGS. 10-13. Thestructure and function of main pump 20 and main pump end cap 22 is aspreviously described for hydraulic pump assembly 10 and will not befurther described herein. The only differences between auxiliary pump 40and auxiliary pump 140 are in the orientation of their respective inletand outlet ports and passages. In auxiliary pump 40, auxiliary pumpinlet passage 55, and auxiliary pump outlet passage 58 are orientedparallel to auxiliary pump relief passage 61 (with their respectiveports, 46 and 43, on opposite sides of auxiliary pump end cap 42), andalso parallel to the main pump system passages 35 and 36 of main pumpend cap 22. In auxiliary pump 140, the auxiliary pump inlet passage 155and auxiliary pump outlet passage 158 are oriented perpendicular toauxiliary pump relief passage 161 (with their respective ports, 146 and143, located on the same side of auxiliary pump end cap 142), and alsoperpendicular to the main pump system passages 35 and 36 of the mainpump end cap 22. The function of auxiliary pump end cap 142 is the sameas that of auxiliary pump end cap 42. As with the first embodiment, theauxiliary pump inlet passage 155 feeds both the charge pump 184 andauxiliary pump 140, and the auxiliary pump relief passage 161 dischargesfluid to an external reservoir or cooler (not shown) via auxiliary pumprelief port 144.

A third representative hydraulic pump assembly 210 having auxiliary pump240 assembled to main pump 20 is depicted in FIGS. 14-17. The structureand function of main pump 20 and main pump end cap 22 is as previouslydescribed for hydraulic pump assembly 10 and will not be furtherdescribed herein. Auxiliary pump 240 varies from auxiliary pump 40 inthe orientation of their respective inlet and outlet ports and passages,the location of their respective case drains, and most significantly, inthe manner in which the auxiliary pump relief is treated. When hydraulicfluid of sufficient pressure in auxiliary pump outlet bore 265 cracksauxiliary pump relief valve 245, the fluid is recycled to the auxiliarypump inlet passage 255 via auxiliary pump recycle bore 263, as opposedto passing through auxiliary pump relief passage 261 and out thecorresponding relief port 244, which is now closed with a threadedrelief port plug 262.

As compared to the porting of auxiliary pump 40 previously described,the auxiliary pump inlet passage 255 of auxiliary pump 240 and auxiliarypump outlet passage 258 are oriented perpendicular to its auxiliary pumprelief passage 261 (with their respective ports, 246 and 243, located onopposite sides of auxiliary pump end cap 242), and also perpendicular tothe main pump system passages 35 and 36 of the main pump end cap 22. Asbest illustrated in FIGS. 15 and 17, the case drain 254 of auxiliarypump end cap 242 is relocated (moved 90 degrees relative to the axis ofpump shaft 30 to a position adjacent auxiliary pump inlet passage 255),but continues to drain excess fluid from the auxiliary pump chamber 264to annular passage 278, and ultimately, charge pump arcuate port 74 a.

A fourth representative hydraulic pump assembly 310 having auxiliarypump 340 assembled to main pump 20 is depicted in FIGS. 18-21. Thestructure and function of main pump 20 and main pump end cap 22 is aspreviously described for hydraulic pump assembly 10 and will not befurther described herein. Auxiliary pump 340 varies from the previouslydescribed auxiliary pump 240 in only one regard. The auxiliary pumpinlet passage 355, while remaining parallel to auxiliary pump outletpassage 358, has been reoriented to have its corresponding inlet port346 on the same side of auxiliary pump end cap 342 as that of auxiliarypump outlet port 343. As a consequence, auxiliary pump inlet passage 355has been extended though a bore 355 a in order to provide fluidcommunication with auxiliary pump recycle bore 363. The function ofauxiliary pump end cap 342 is the same as that of auxiliary pump end cap242.

A fifth representative hydraulic pump assembly 410 having auxiliary pump440 assembled to main pump 20 is depicted in FIGS. 22-27. The structureand function of main pump 20 and main pump end cap 22 is as previouslydescribed for hydraulic pump assembly 10 and will not be furtherdescribed herein. The function of auxiliary pump 440 and its end cap 442is substantially the same as that of the previously described auxiliarypumps 240 and 340 and their respective end caps 242 and 342. Theauxiliary pump relief valve 445 recycles hydraulic fluid into theauxiliary pump arcuate port 453 a via a recycle passage 463, which alsocommunicates with charge pump arcuate port 456 in pocket 416. However,the auxiliary pump end cap 442 has been simplified, taking advantage ofmodern casting techniques to form the porting, as opposed to machiningtechniques (as evident in the straight bores and right angleintersections of porting in auxiliary pump end caps 42, 142, 242 and342). Consequently, the equivalent of auxiliary pump relief passages 261and 361, their corresponding relief ports, 244 and 344, and threadedplugs, 262 and 362, which were necessary to machine auxiliary pumprecycle bores 263 and 363, are no longer needed to form a fluid passageconnecting the auxiliary pump relief to the auxiliary pump arcuate port453 a. Recycle passage 463 may be formed directly by a castingoperation.

Other differences between auxiliary pump end cap 442 and auxiliary pumpend caps 242 and 342 include the routing of the case drain 454 and theorientation of the porting in general. As best viewed in FIGS. 25-27,excess fluid build-up in the auxiliary pump chamber 464 is directed tothe auxiliary pump inlet passage 455 via case drain 454. This excessfluid is no longer routed to the annular passage 478, and ultimately, tothe charge pump arcuate port 74 a. The porting of auxiliary pump end cap442 is generally oriented parallel to the main pump system passages 35and 36, the auxiliary pump inlet port 446 and auxiliary pump outlet port443 being located on the same side of the auxiliary pump end cap 442,and adjacent system ports 26 and 27.

A sixth representative hydraulic pump assembly 510 having auxiliary pump540 assembled to a main pump 520 is depicted in FIGS. 28-33. Auxiliarypump 540 is distinguishable from previously depicted embodiments in thatthe discharge of auxiliary pump relief valve 545 is routed through themain pump drain port 538. In addition to the modifications enumeratedbelow, auxiliary pump end cap 542 varies from the previous fiveembodiments by utilizing only three fasteners 529 to mate it to mainpump end cap 522 and main pump housing 21. This represents a materialand machining savings, and permits a reduced-length fastener 519 (ascompared to fastener 529) to complete the joining of main pump end cap522 and main pump housing 21. The structure and function of main pump520 and main pump end cap 522 is as previously described for main pump20 and main pump end cap 22, except an additional drain passage 566 hasbeen added to main pump end cap 522 to receive the discharge ofauxiliary pump relief valve 545.

In FIG. 33, a portion of main pump housing 21 has been cut away toreveal a sump 512 in fluid communication with drain passage 539 and,thereafter, drain port 538. This typical arrangement provides a pathwayfor accumulated hydraulic fluid from the main pump 520 to an externallocation (not shown), such as a reservoir used for cooling. Additionaldrain passage 566 places drain port 538 in communication with theinterface between main pump end cap 522 and auxiliary pump end cap 542.Similarly, an additional drain passage 567 in auxiliary pump end cap 542places auxiliary pump relief passage 561 in communication with theinterface between main pump end cap 522 and auxiliary pump end cap 542.A tubular connector 568 joins the additional drain passages 566 and 567to complete the pathway from auxiliary pump relief passage 561 to drainport 538. An integral, annular sealing feature 568 a at each end oftubular connector 568 is pressed into the counterbore of each additionaldrain passage 566 and 567 upon assembly, sealing the pathway andeliminating a fluid restriction. It should be understood that othersealing methods known in the art, such as the use of a pair of o-ringswith a straight bore connector, may also be used. When fluid pressure inauxiliary pump outlet passage 558 and auxiliary pump outlet bore 565 issufficient to crack auxiliary pump relief valve 545, hydraulic fluid isrelieved through drain port 538. FIG. 33 also depicts a perimeter seal514 that seals main pump housing 21 against main pump end cap 522. Seal514 may require a higher pressure rating than similar seals (not shown)employed in the other hydraulic pump assemblies illustrated herein. Thischange in seal rating is intended to counter any additional casepressure that may momentarily build in sump 512 when auxiliary pumprelief valve 545 is opened.

To ensure the necessary vertical alignment of case drain port 538 andauxiliary pump relief passage 561, auxiliary pump outlet passage 558 andinlet passage 555 occupy a parallel configuration similar to thatdepicted in auxiliary pump end cap 242. However, as compared to theporting of auxiliary pump end cap 242, the positions of auxiliary pumpoutlet passage 558 and inlet passage 555 are reversed and also rotated90 degrees clockwise about pump shaft 30 relative to main pump end cap522. Auxiliary pump relief passage 561, in intermittent fluidcommunication with auxiliary pump outlet passage 558 and outlet bore565, is generally disposed perpendicular thereto, and thus appropriatelyaligned relative to case drain port 538. To accommodate the relativerotation and juxtaposition of auxiliary pump outlet passage 558 andinlet passage 555, the porting on running surface 552 is rotated 90degrees counterclockwise about pump shaft 30 relative to main pump endcap 522. Auxiliary pump housing 541 is similarly rotated to ensure thatthe appropriate displacement angle of thrust bearing 551 is maintained.

The versatility of the present invention is further illustrated byhydraulic pump assembly 510, wherein main pump housing 21 and trunnionarm 23 are rotated 180 degrees about pump shaft 30 relative to main pumpend cap 522. This permits variability in the routing of control linkagesto the main pump 520. From the above discussion, it should be understoodthat the variable arrangement of the ports and passages of the auxiliarypump end caps depicted herein demonstrates that the invention may beadapted to meet the constraints of a given application.

Similar to auxiliary pump 440, excess fluid build-up in auxiliary pumpchamber 564 is directed to the auxiliary pump inlet passage 555 viaauxiliary pump case drain 554. Such fluid is then available to feedauxiliary pump 540 by way of auxiliary pump arcuate port 553 a or chargepump 584 via the charge pump arcuate port 556 located in pocket 516. Thedischarged fluid from auxiliary pump 540 exits auxiliary pump arcuateport 553 b, traverses auxiliary pump outlet passage 558 and is availablefor external service via auxiliary pump outlet port 543. Hydraulic fluidreturning from external service enters via auxiliary pump inlet port 546and is once again directed to the auxiliary pump inlet passage 555. Thedischarged fluid from charge pump 584 exits charge pump arcuate port 574b and enters charge gallery 576. As previously described for hydraulicpump assembly 10, this charged fluid may be relieved through charge pumprelief valve 75, utilized as make-up fluid by main pump 520 throughcheck/relief valves 25, or bled to sump 512 via bleed passage 580.

A seventh representative hydraulic pump assembly 610 having auxiliarypump 640 assembled to a main pump 20 is depicted in FIGS. 34-40. Thedistinguishing features of auxiliary pump 640 and auxiliary pump end cap642 are the vertically oriented auxiliary pump inlet port 646 and outletport 643. Unlike the ports of the other auxiliary pump embodimentsdepicted herein, auxiliary pump inlet port 646 and outlet port 643 areformed on the horizontal face of end cap 642 adjacent auxiliary pumprunning surface 652. Consequently, inlet port 646 intersects auxiliarypump inlet passage 655, and outlet port 643 intersects auxiliary pumpoutlet passage 658, in a generally perpendicular orientation. Because ofthe machining required to completely form auxiliary pump inlet passage655 and outlet passage 658, the openings remaining in the vertical facesof auxiliary pump end cap 642 are closed with threaded plugs 669 a and669 b, respectively. As previously described for auxiliary pump end cap542, the geometry of auxiliary pump end cap 642 is such that only threefasteners 629 are required to mate it to main pump end cap 22 and mainpump housing 21, while a fourth, reduced-length fastener 619 completesthe joining of main pump end cap 22 and main pump housing 21.

The structure and function of main pump 20 and main pump end cap 22 areas previously described for hydraulic pump assembly 10 and will not befurther described herein. It should be noted that while main pumphousing 21 and trunnion arm 23 are depicted in the same rotationalorientation relative to main pump end cap 22 as previously described forhydraulic pump assembly 510, the orientation of these components inhydraulic pump assembly 610 could be that illustrated for the first fiveembodiments depending on the requirements of a given application.

The structure and function of elements of auxiliary pump 640 and its endcap 642 are substantially similar to those of the previously describedauxiliary pumps and their respective end caps. For instance, auxiliarypump relief valve 645 recycles hydraulic fluid into the auxiliary pumpinlet passage 655 via a recycle bore 663 in communication with auxiliarypump outlet passage 658. This is similar to the porting schemes depictedin auxiliary pump end caps 242, 342, and 442, respectively. And similarto auxiliary pumps 440 and 540, excess fluid build-up in the auxiliarypump chamber 664 is directed to the auxiliary pump inlet passage 655 viaa case drain 654. Hydraulic fluid present in the auxiliary pump inletpassage 655 is then available to feed auxiliary pump 640 by way ofauxiliary pump arcuate port 653 a or to feed charge pump 684 via chargepump arcuate port 656 located in pocket 616. The discharge fromauxiliary pump 640 exits auxiliary pump arcuate port 653 b, traversesauxiliary pump outlet passage 658 and is available for external servicevia auxiliary pump outlet port 643. Hydraulic fluid returning fromexternal service enters via auxiliary pump inlet port 646 and is onceagain directed to the auxiliary pump inlet passage 655. The dischargedfluid from charge pump 684 exits charge pump arcuate port 74 b andenters charge gallery 76. As previously described for hydraulic pumpassembly 10, this charged fluid may be relieved through charge pumprelief valve 75, utilized as make-up fluid by main pump 20 throughcheck/relief valves 25, or bled to sump (not shown) via bleed passage80.

The auxiliary pump inlet passage 655 and the auxiliary pump outletpassage 658 are generally aligned in parallel with each other and themain pump system passages 35 and 36. They are disposed on opposite sidesof pump shaft 30. Auxiliary pump inlet passage 655 and auxiliary pumpoutlet bore 665 (an extension of auxiliary pump outlet passage 658) areintersected by auxiliary pump recycle bore 663 in a generallyperpendicular orientation. The respective ports of auxiliary pump inletpassage 655 and outlet passage 658, i.e. auxiliary pump inlet port 646and auxiliary pump outlet port 643, are located on opposite sides ofauxiliary pump housing 641.

Auxiliary pump arcuate port 653 a (inlet port) and arcuate port 653 b(outlet port) on auxiliary pump running surface 652 are disposed in theopposite orientation as those arcuate ports of auxiliary pump runningsurface 552. Consequently, auxiliary pump housing 641 is rotated 180degrees about the rotational axis of pump shaft 30 as compared toauxiliary pump housing 541. This is to ensure that the appropriatedisplacement angle of thrust bearing 651 is maintained.

An eighth representative hydraulic pump assembly 710 having auxiliarypump 740 assembled to a main pump 20 is depicted in FIGS. 41-44. Thestructure and function of main pump 20 and main pump end cap 22 is aspreviously described for hydraulic pump assembly 10 and will not befurther described herein.

The structure and function of elements of auxiliary pump 740 and its endcap 742 are substantially similar to those of previously describedauxiliary pump 640 and its respective end cap 642, and as such will notbe detailed herein. The chief difference between auxiliary pumps 740 and640 is the simplification of end cap 742 through the use of castingtechniques, permitting auxiliary pump recycle bore 763, inlet passage755, and outlet passage 758 to be integrally formed thereby without theneed for a machined cross-passage which must then be plugged. Ascompared to auxiliary pump end cap 642, these casting techniques reducethe amount of material and machining necessary to form auxiliary pumpend cap 742.

Auxiliary pump end cap 742 has a vertically oriented inlet port 746 anda vertically oriented outlet port 743. Inlet port 746 intersectsauxiliary pump inlet passage 755, and outlet port 743 intersectsauxiliary pump outlet passage 758, in a generally perpendicularorientation. Additionally, the geometry of auxiliary pump end cap 742 issuch that it may be secured to main pump end cap 22 and main pumphousing 21 by means of two threaded fasteners 729, rather than the threeor four threaded fasteners required for the previous embodimentsdepicted herein. This represents a further reduction in the amount ofmaterial needed to form auxiliary pump end cap 742, and permits the useof two, reduced-length fasteners 719 to complete the joining of mainpump end cap 22 and main pump housing 21.

A ninth representative hydraulic pump assembly 810 having a auxiliarypump 840 assembled to a main pump 820 is depicted in FIG. 45. Thestructure and function of elements of auxiliary pump 840 and its end cap842 are substantially similar to those of previously described auxiliarypump 740 and its respective end cap 742, and as such will not bedetailed herein. The distinguishing feature of auxiliary pump end cap842 is the inclusion of both vertically and horizontally oriented inletand outlet ports. Vertical inlet port 846 a intersects auxiliary pumpinlet passage 855, and vertical outlet port 843 a intersects auxiliarypump outlet passage 858, in a generally perpendicular orientation.Additionally, auxiliary pump end cap 842 has a horizontally orientedinlet port 846 b in line with auxiliary pump inlet passage 855, and ahorizontally oriented outlet port 843 b in line with auxiliary pumpoutlet passage 858. This feature adds versatility to the manner in whichauxiliary pump 840 may be applied to a vehicle or other equipment, usingeither vertically or horizontally oriented fittings and hoses (notshown). The non-selected ports depicted in FIG. 45, horizontal inletport 846 b and horizontal outlet port 843 b, may be sealed with threadedplugs 869 a, 869 b, respectively.

Another distinguishing feature of hydraulic pump assembly 810 is the useof two threaded fasteners 885 to attach auxiliary pump end cap 842directly to main pump end cap 822, permitting main pump end cap 822 tobe preassembled to main pump housing 21 with four, reduced-lengthfasteners 819. This configuration introduces more flexibility in the useof main pump 820, allowing it to be alternately fitted with either asimple gerotor charge pump and cover (not shown), or the presentinvention's auxiliary pump and embedded charge pump.

Other than the addition of two threaded bores (not shown) in main pumpend cap 822 for receiving threaded fasteners 885, the structure andfunction of main pump 820 and main pump end cap 822 is as previouslydescribed for main pump 20 and main pump end cap 22, respectively, andwill not be further described herein.

A tenth representative hydraulic pump assembly 910 having auxiliary pump940 assembled to main pump 20 is depicted in FIGS. 46-49. The structureand function of main pump 20 and main pump end cap 22 can be aspreviously described for hydraulic pump assembly 10 and will not befurther described herein.

The structure and function of elements of auxiliary pump 940 and its endcap 942 are substantially similar to those of previously describedauxiliary pump 740 and its respective end cap 742 and as such will notbe detailed herein. The chief differences between auxiliary pumps 940and 740 are the structure of auxiliary pump relief valve 945 and thelocation of auxiliary relief valve port 960. Auxiliary pump relief valve945 is a two-function valve of the type described in U.S. Pat. No.6,719,005, the disclosure of which is incorporated herein by reference,but valve 945 does not have a bleed orifice in the valve seat 945 c. Inaddition to its relief function, valve 945 incorporates a make-up fluidbypass function. In order to employ this two-function valveappropriately, auxiliary relief valve port 960 has been relocated to theopposite side of auxiliary pump end cap 942 as compared to, e.g., endcap 742. This orientation exposes the aft portion of valve 945 to theoutlet or high pressure side of the auxiliary pump hydraulic circuit,and exposes the fore portion of valve 945 to the inlet pressure residentin auxiliary pump recycle passage 963.

Referring to FIG. 49, the relief function of auxiliary pump relief valve945 is engaged when the outlet pressure resident in auxiliary reliefvalve port 960 (and correspondingly present in auxiliary pump outletbore 965 and auxiliary pump outlet passage 958) is of sufficientmagnitude to act upon valve guide 945 f and the rearmost portion ofvalve stem 945 e to overcome the spring force of relief compressionspring 945 b and pressure resident in auxiliary pump inlet passage 955,thereby opening valve 945 in a first manner. This can be more simplydescribed as the pressure in auxiliary pump outlet passage 958 exceedinga first set pressure. As a result, valve stem 945 e is unseated fromvalve seat 945 c and opens a pathway 945 g between the high pressure andlow pressure sides of the auxiliary pump hydraulic circuit. Hydraulicfluid is thus recycled to auxiliary pump inlet passage 955 via auxiliarypump recycle passage 963. Such high pressure situations may occur whenthe load on the auxiliary device increases unexpectedly.

The make-up fluid bypass function of auxiliary pump relief valve 945 isbest understood in the context of applying hydraulic pump assembly 910to a vehicle having an auxiliary device, e.g. a lawn tractor having amower deck lift. A vehicle 901 is shown schematically in FIG. 50 whereinhydraulic pump assembly 910 is driven by prime mover 902. It is to beunderstood that the vehicle 901 illustrated in FIG. 50 is but one ofmany applications for hydraulic pump assembly 910 in accordance with theprinciples of the invention. Hydraulic fluid is drawn from reservoir 906through a mesh screen filter 907 to feed auxiliary pump 940 and chargepump 984. Main pump 20, whose closed-loop hydraulic circuit ismaintained by charge pump 984, supplies hydraulic fluid to power one ormore traction motors 903. Correspondingly, auxiliary pump 940 supplieshydraulic fluid to power one or more auxiliary devices 904. Hydraulicfluid powering the auxiliary devices 904 may circulate through anoptional oil cooler 905 and filter 908 on its way back to reservoir 906,which also receives hydraulic fluid losses from main pump 20 andtraction motors 903.

If the auxiliary pump 940 is not being driven by prime mover 902 (i.e.vehicle 901 is shut down) and an operator wishes to return the auxiliarydevice 904 to its non-driven state or position (e.g., lower the mowerdeck to ground level), the operator's release of hydraulic fluid fromthe high pressure side of the auxiliary pump hydraulic circuit toreservoir 906 may create a relative vacuum or suction on the highpressure side of auxiliary pump 940. This can be problematic in that theauxiliary device's return to the non-driven state or position may not befully accomplished or may be unnecessarily slowed. For example, in thecase of end cap 742 as shown in FIG. 44, relief ball 745 c would remainseated under the influence of the relative vacuum or suction. As aresult, oil or possibly entrained air in auxiliary pump chamber 764 maybe pulled through auxiliary pump 740 into the auxiliary pump hydrauliccircuit. Upon resumption of operation, entrained air or the relativevacuum may lead to erratic performance of the auxiliary device.

The make-up fluid bypass function of valve 945 counteracts thissituation. End cap 942 and valve 945 permit make-up fluid to be drawnfrom reservoir 906, to bypass auxiliary pump 940, and to replace thehydraulic fluid evacuated from the high pressure side of the auxiliarypump hydraulic circuit. Specifically, auxiliary pump relief valve 945has a valve seat 945 c disposed about one end of valve stem 945 e. Inits closed position, valve seat 945 c prevents fluid communicationbetween auxiliary pump recycle passage 963 and auxiliary pump outletbore 965. However, in the case of a relative vacuum or suction presentin auxiliary relief valve port 960 (and correspondingly present inauxiliary pump outlet bore 965 and auxiliary pump outlet passage 958),valve seat 945 c will be unseated from the opening 963 a to auxiliarypump recycle passage 963, under the influence of fluid pressure inpassage 963 and in opposition to the relatively light spring force ofbypass compression spring 945 d, thereby opening valve 945 in a secondmanner. This can be more simply described as the pressure in auxiliarypump outlet passage 958 decreasing below a second set pressure. Thus,hydraulic fluid bypasses auxiliary pump 940 to fill the void created onthe high pressure side of the auxiliary pump hydraulic circuit andimprove performance.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teaching of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention.

What is claimed is:
 1. A hydraulic pump assembly, comprising: a firsthydraulic porting member comprising a first face and a second face onopposite sides of the first hydraulic porting member, wherein the firstface is engaged to a main pump housing to form a sump; a secondhydraulic porting member comprising a third face and a fourth face onopposite sides of the second hydraulic porting member; a charge pumprotatably disposed on the second face; an auxiliary pump housing engagedto the fourth face to form an auxiliary pump chamber and an auxiliarypump located in the auxiliary pump chamber; and a charge pump reliefvalve located in a charge relief passage, and comprising a ball and aspring, wherein the spring is retained between a valve seat in thecharge relief passage and the second hydraulic porting member.
 2. Ahydraulic pump assembly, comprising: a first hydraulic porting memberjoined to a second hydraulic porting member, the first hydraulic portingmember comprising a pair of system ports; a primary pump engaged to afirst side of the first hydraulic porting member; a charge pump disposedbetween the first hydraulic porting member and the second hydraulicporting member; and an auxiliary pump disposed on the second hydraulicporting member, the second hydraulic porting member, wherein the secondhydraulic porting member comprises: an auxiliary inlet port connected toan auxiliary inlet passage and an auxiliary outlet port connected to anauxiliary outlet passage; a first arcuate port connecting the auxiliarypump to the auxiliary inlet passage and a second arcuate port connectingthe auxiliary pump to the auxiliary outlet passage; an auxiliary reliefvalve disposed in an auxiliary relief port, wherein the auxiliary reliefport is connected to the auxiliary outlet passage; and a recycle passagecast entirely within the second hydraulic porting member and connectingthe auxiliary inlet passage to the auxiliary relief port.
 3. Thehydraulic pump assembly of claim 2, further comprising a case drainpassage extending from the auxiliary inlet passage to an externalsurface of the second hydraulic porting member.
 4. A hydraulic pumpassembly, comprising: a first hydraulic porting member joined to asecond hydraulic porting member; a primary pump engaged to a first sideof the first hydraulic porting member, the first hydraulic portingmember comprising a pair of system ports connected to a drive apparatusand to the primary pump; a charge gallery hydraulically connected to theprimary pump and sealed from any external access; a charge pump disposedbetween the first hydraulic porting member and the second hydraulicporting member, wherein the charge pump receives hydraulic fluid from acharge pump inlet and provides charged hydraulic fluid to the chargegallery; a charge relief passage hydraulically connected only betweenthe charge gallery and the charge pump inlet; and an auxiliary pumpdisposed on the second hydraulic porting member, the second hydraulicporting member comprising an auxiliary inlet port connected to anauxiliary inlet passage, and an auxiliary outlet port connected to anauxiliary outlet passage, wherein the auxiliary inlet passage providesfluid to both the auxiliary pump and the charge pump.
 5. The hydraulicpump assembly of claim 4, wherein the charge gallery is sealed from anyexternal access by means of a port plug.
 6. The hydraulic pump assemblyof claim 4, further comprising a charge pump relief valve located in thecharge relief passage, and comprising a ball and a spring, wherein thespring is retained between a valve seat in the charge relief passage andthe second hydraulic porting member.
 7. The hydraulic pump assembly ofclaim 4, wherein the primary pump, the charge pump and the auxiliarypump share a common axis of rotation.
 8. The hydraulic pump assembly ofclaim 7, further comprising a single input shaft that is engaged to anddrives the primary pump, the charge pump and the auxiliary pump.
 9. Thehydraulic pump assembly of claim 4, wherein the second hydraulic portingmember further comprises: a first arcuate port connecting the auxiliarypump to the auxiliary inlet passage and a second arcuate port connectingthe auxiliary pump to the auxiliary outlet passage; an auxiliary reliefvalve disposed in an auxiliary relief port, wherein the auxiliary reliefport is connected to the auxiliary outlet passage; and a recycle passageconnecting the auxiliary inlet passage to the auxiliary relief port. 10.The hydraulic pump assembly of claim 9, wherein the recycle passage iscast entirely within the second hydraulic porting member.
 11. Ahydraulic pump assembly use with a plurality of external hydraulicdevices, the hydraulic pump assembly comprising: a primary propulsionpump, a charge pump and an auxiliary pump, wherein the primarypropulsion pump, the charge pump and the auxiliary pump share a commonaxis of rotation; a pair of system ports connected to the primarypropulsion pump and configured to be hydraulically connected to a firstexternal hydraulic device; an auxiliary output configured to beconnected to a second external hydraulic device, whereby pressurizedfluid may be transmitted from the auxiliary pump to the second externalhydraulic device; and an auxiliary inlet configured to be connected tothe second external hydraulic device, and fluidly connected to anauxiliary inlet passage, wherein the auxiliary inlet passage provides asource of fluid for both the auxiliary pump and the charge pump; whereinthe hydraulic pump assembly is configured such that the primarypropulsion pump receives hydraulic fluid only from one of the pair ofsystem ports and from the charge pump.
 12. The hydraulic pump assemblyof claim 11, further comprising a charge gallery disposed between andhydraulically connected to both the charge pump and the primarypropulsion pump, wherein the charge pump provides hydraulic fluid to thecharge gallery and the primary propulsion pump receives hydraulic fluidfrom the charge gallery.
 13. The hydraulic pump assembly of claim 12,wherein the charge pump is disposed between the auxiliary pump and theprimary propulsion pump.
 14. The hydraulic pump assembly of claim 11,further comprising a single input shaft that is engaged to and drivesthe primary propulsion pump, the charge pump and the auxiliary pump. 15.The hydraulic pump assembly of claim 11, further comprising a chargerelief passage, and a charge relief valve located in the charge reliefpassage, the charge relief valve comprising a ball and a spring.